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Translational diffusion and fluid domain connectivity in a two-component, two-phase phospholipid bilayer.
W L Vaz1, E C Melo, T E Thompson
1Max-Planck-Institute für Biophysikalische Chemie, Göttingen, Federal Republic of Germany.
Biophysical Journal
|November 1, 1989
Summary
Mixed phospholipid bilayers show a gel phase disconnecting a liquid crystalline phase across a broad concentration range. This connectivity impacts biological membrane organization and domain shape.
Area of Science:
- Biophysics
- Materials Science
Background:
- Phospholipid bilayers are fundamental to cell membrane structure.
- Understanding phase coexistence in lipid mixtures is crucial for membrane function.
Purpose of the Study:
- To investigate the two-dimensional connectivity of mixed dimyristoyl phosphatidylcholine (DMPC) and distearoyl phosphatidylcholine (DSPC) bilayers.
- To analyze how composition and temperature affect phase connectivity in these lipid mixtures.
Main Methods:
- Utilized fluorescence recovery after photobleaching (FRAP) to study bilayer connectivity.
- Employed N-nitrobenzodiazolyl-dilauroyl phosphatidylethanolamine (NBD-DLPE) as a fluorescent probe, which preferentially partitions into the liquid crystalline phase.
Main Results:
- Observed peritectic behavior with a significant region of coexisting gel and liquid crystalline phases.
- Found the connectivity line to be near the liquidus line on the phase diagram.
- Demonstrated that a gel phase (approx. 20%) disconnects a liquid crystalline phase (approx. 80%) over a wide concentration range.
Conclusions:
- The observed phase connectivity has implications for domain shape within lipid bilayers.
- This connectivity influences the organization of components in biological membranes.